The Broad-Complex (Br-C) is a Drosophila regulatory gene. Its transcription is controlled by a steroid hormone (20-hydroxyecdysone). The Br-C encodes a set of four DNA-binding Zn finger proteins (Z1, Z2, Z3, Z4) that participate in the hierarchial transcriptional regulation essential for metamorphosis. The Br-C is one of at least such genes that govern metamorphosis. Different Zn finger proteins are produced by the Br-C through differential splicing of Zn finger coding exons to a common "core." Our current results demonstrate that different Br-C Zn finger proteins have different roles in metamorphosis, but they may also be functionally related in a redundant, cooperative and/or competitive manner. Other evidence suggests that the locus may regulate itself both positively and negatively. Additionally, some proteins are expressed in some tissues but not in others, e.g. Z2 and Z4 are transcribed in imaginal disc but not in salivary gland. Finally, the timing of expression of the different transcripts within a given tissue differs. The studies we propose are intended to illuminate the roles this gene and its component parts have in the propagation of a complex hormonally regulated developmental process. Accordingly, we propose to define the functional relationships between Br-C proteins through mutant analyses and induced expression of different Zn finger proteins. A most important objective is to investigate possible autoregulation and cross-regulation at the locus. These studies will be facilitated by the systematic in situ mutagenic dissection of the Br-C to produce mutants that on the one hand, are true null mutations for each Zn finger domain, or, on the other hand, can express only one Zn finger protein. These studies will help to describe the general nature of hormone control of gene expression and development.